[PATCH v2] ima: Fix stack-out-of-bounds in is_bprm_creds_for_exec()

[Mimi Zohar]

Hi Chris,

On Sun, 2025-12-21 at 12:01 -0600, Chris J Arges wrote:
> KASAN reported a stack-out-of-bounds access in ima_appraise_measurement
> from is_bprm_creds_for_exec:
> 
> BUG: KASAN: stack-out-of-bounds in ima_appraise_measurement+0x12dc/0x16a0
>  Read of size 1 at addr ffffc9000160f940 by task sudo/550
> The buggy address belongs to stack of task sudo/550
> and is located at offset 24 in frame:
>   ima_appraise_measurement+0x0/0x16a0
> This frame has 2 objects:
>   [48, 56) 'file'
>   [80, 148) 'hash'
> 
> This is caused by using container_of on the *file pointer. This offset
> calculation is what triggers the stack-out-of-bounds error.
> 
> In order to fix this, pass in a bprm_is_check boolean which can be set
> depending on how process_measurement is called. If the caller has a
> linux_binprm pointer and the function is BPRM_CHECK we can determine
> is_check and set it then. Otherwise set it to false.
> 
> Fixes: 95b3cdafd7cb7 ("ima: instantiate the bprm_creds_for_exec() hook")
> 
> Signed-off-by: Chris J Arges <carges at cloudflare.com>

Thank you!  I'd appreciate your limiting the line lengths to 80 chars (e.g.
scripts/checkpatch.pl --max-line-length=80).

-- 
thanks,

Mimi